WEST System 407 Low Density Filler

West System 407 Low-Density filler is a blended microballoon-based filler used to make fairing putties that are easy to sand or carve. Reasonably strong on a strength-to-weight basis. Cures to a dark red/brown color.

2013-09-09TOM CAHN asked:can the #407 filler be mixed with Polyester resin to be used as a fairing compound?

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2013-09-09GORDON FRISBEY:Yes. I have used the West fillers many times and they all do well.

2013-09-09tom cahn:Gordon,
Thank you Very much,
Tom

2013-09-09JIM MEEKS:Yes it can. But what you will end up with is expensive "Bondo." That's all Bondo is. In addition, polyester resin has only a fraction of the strength and water-resistance of epoxy. It simply will not adhere for any length of time. It will also start to cure much faster, even if you reduce the amount of MEK.

2013-09-09CAROLE ROBERTS:I do not know if it works with polyester resin. My experience has been to mix it with sifted sawdust and add to the West Epoxy resin & hardener to repair cracks in a log cabin.

2013-09-09WILLIAM CZAJKA:Maybe, but it seems like you would be better off using a purpose made fairing compound, like Quickfair.

2013-02-03A shopper asked:I just finished a 7 year restoration of my 79 CVX20. The bottom has a 3/16" hook. I don't want to flip it for repair. What materials should I use? About 30 years ago I repaired a lot worse hook with fiberglass matt. Surely, someone has a method that is easier than that.

2012-11-12DAVID BRYANT LAST NAME asked:I'm in the process of repairing and fairing blisters on my sailboat. I ground out the blisters 5 months ago and let the bottom dry out thoroughly. Today began sealing the holes with West system epoxy not realizing that I'm supposed to apply thickened filler while the epoxy is still in the "gel" stage. I need to order Wet 407 or 410 then go over the holes I just sealed with the thickened mixture to fair the hull. Since by then the layer I just applied will be fully cured, do I need to grind out the blisters again of can I just re-apply epoxy the fill with thickened mixture while this application is still in the gel stage?

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2012-11-12CAROLE ROBERTS:My experience with the West System has been involved with repairs to a log cabin, but I have had 20 years or more of work with various epoxy products. I have found that a good, stabilized base is critical for the success of the final layer. My thoughts are that the epoxy sealant would remain strong if you left it as is, but if you were to try to adhere a layer with fairing without preparing a good base, it would eventually "flip" off due to temperature reactions between the hull and water.
While I have not had any actual experience with a boat hull, I might not grind out the entire sealant base, but, I would make an effort to considerably rough up the base, especially near the surface layer in order to give the filler base a good gripping bond. I don't know how large the holes are, but think like a dentist and do a bit of undercutting to allow a better grip. Good luck---it is all a learning process.

2012-11-12JOHN C HUMPHREY:David,
There is a blush of wax left on the surface when the resin is fully cured. This needs to be sanded off before a new coat of anything is applied to it. If the surface you have is fairly smooth it is easy enough. If it is too rough you may need to do a bit of grinding. The sanding also provides a mechanical key for the epoxy to adhere to.
John

2012-11-12ALAN MCWHIRTER:I would sand the cured epoxy with 80 grit paper to roughen the surface, mix up a batch of epoxy and add 407 to the pot to a fairly stiff consistence and apply to the sanded surfaces. No need to grind out the blisters again.

2012-11-12David Bryant Last Name:Thanks! You saved my life. I was up all night worrying about this.

2012-11-12ALAN MCWHIRTER:You are welcome! Good luck with the repair.
Alan

2012-11-12JIM MEEKS:No, you don't need to grind the blister holes again. I would, however, lightly sand the holes (really the epoxy you have already applied) with 80-100 grit paper just to rough up the surface a little. Then wipe the holes with acetone or your particular favorite solvent that fully evaporates. Hit the holes again with a clean cloth just to be sure. You are then ready to go. Suggestion: Don't use a "squeegee" that is too flexible. You will end up with concave hole repair instead of flat. Good luck. The West products are excellent.

2012-11-13MARK FRUEHAUF:David
You should consult directly with the folks at West about this.
They are very helpful. My guess is if the first layer is fully cured you may be able to wash it and just lightly sand it before applying the 2nd coat.
I hope that is helpful.
Mark

2012-11-13KEVIN COBB:Filler is generally added as soon as the resin and hardener have been stirred completely. Low density filler being used for blister repair should be brought to a consistency a little thicker than peanut butter or thick enough to fill the hole and hang without dripping or sagging. The purpose for the filler is to make the repair easier to sand and fair as well as having less weight than solid epoxy. You won't need to re-grind or remove the ones you've done but you will find that they will be more difficult to fair.

2011-10-20A shopper asked:Can this be used as a conductive mixture in harsh environments?

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2011-10-21CAROLE ROBERTS:Sorry, unable to help---have not yet used the product.

I used this to achieve final contours on the front edge fairing of an airplane canopy. It worked VERY well ... mixes well, easy to smooth into minor surface irregularities, and sands more readily than microballoons.

Use in places you want to fair. I used this on fiberglass boats above and below the waterline. This wets out well and adheres well. It is a bit harder than 410 but spreads out to really fine edge. You can mix any of the West System fillers to get just the right mix you need any job.